Oxygen tension and collagen deposition were measured in standardized, subcutaneous wounds in 33 postoperative surgical patients. Pertinent clinical and wound parameters were analyzed by Pearson's correlation test and sequential linear regression analysis. Collagen deposition was directly and significantly proportional to wound oxygen tension and measures of perfusion. There were no significant correlations with hematocrit, estimated blood loss, length of operation, smoking, age, weight, sex, or urine output. This study in humans confirms animal experiments showing that collagen deposition and tensile strength in wounds are limited by perfusion and tissue oxygen tension. It appears unnecessary to maintain hemoglobin at normal levels to support repair, provided that peripheral perfusion can be maintained at a high level in compensation for anemia. These circumstances reflect the fact that although oxygen is essential to many aspects of healing, and must be delivered at adequate partial pressures, reparative tissue consumes relatively little of it.